An optical disk is a data storage medium which is readable by a laser-based reading device. Optical disks known as "compact disks" or "CDS" have become increasingly popular during the last decade for recording music and audio-visual works. Due to the large storage capacity of optical disks as compared to conventional magnetic storage media, optical disks known as "ROM disks" have become popular for storing computer readable information. However, until very recently, optical disks were of somewhat limited use in the computer industry due to the fact that optical disks could not be erased and written with new information, i.e., ROM disks are "read only" memory devices. However, recent technology has produced optical disks which are both computer readable and computer writeable. Consequently, optical disks are becoming increasingly important in the computer industry and may eventually replace magnetically readable and writeable storage media such as floppy disks and hard disks. Another recent development, the ability to provide data storage on both surfaces on an optical disk, has effectively doubled the storage capacity of the optical disk. Optical disks of the type used in computer applications are generally mounted in parallelepiped-shaped cartridges. Also used in the computer industry for data storage are parallelepiped-shaped tape cartridges such as Digital Audio Tape (DAT) cartridges and 8 mm tape cartridges.
The increasing popularity of such data storage cartridges in the computer field has spurred the development of many different types of automated cartridge handling systems for storing the cartridges at known locations and for retrieving a desired cartridge from a storage location and inserting the cartridge into a cartridge reading device, such as a tape or disk drive. Generally speaking, such a cartridge handling system may include a cartridge storage system for storing the cartridges at corresponding storage locations and a cartridge engaging assembly for retrieving a desired cartridge from its corresponding storage location, transporting the cartridge to a cartridge reading device, such as a disk or tape drive, and inserting the cartridge into the drive. The cartridge engaging assembly may also remove a cartridge from a drive, move the cartridge into alignment with its storage location, and return the cartridge to its storage location.
Various features and components of cartridge handling systems and cartridge engaging assemblies are disclosed in U.S. Pat. Nos. 4,944,082 for METHOD OF PROVIDING A SHEET METAL HOUSING WITH PRECISELY POSITIONED MOUNTING REFERENCES of Jones et al.; 4,998,232 for OPTICAL DISK HANDLING APPARATUS WITH FLIP LATCH of Methlie et al.; 5,014,255 for OPTICAL DISK CARTRIDGE HANDLING APPARATUS WITH PASSIVE CARTRIDGE ENGAGEMENT ASSEMBLY of Wanger, et al.; 5,010,536 for CARTRIDGE HANDLING SYSTEM of Wanger et al.; 5,043,962 for CARTRIDGE HANDLING SYSTEM of Wanger, et al.; 5,062,093 for OPTICAL DISK INSERTION APPARATUS of Christie, et al.; 5,101,387 for LATERAL DISPLACEMENT CONTROL ASSEMBLY FOR AN OPTICAL DISK HANDLING SYSTEM of Wanger, et al.; 5,184,336 for LATERAL DISPLACEMENT CONTROL ASSEMBLY FOR AN OPTICAL DISK HANDLING SYSTEM of Wanger, et al.; 5,596,556 for LINEAR DISPLACEMENT AND SUPPORT APPARATUS FOR USE IN A CARTRIDGE HANDLING SYSTEM of Luffel, et al.; and 5,638,349 for CARTRIDGE HANDLING SYSTEM WITH DUAL CARTRIDGE ENGAGING ASSEMBLY, which are each hereby specifically incorporated by reference for all that is disclosed therein.
Many cartridge handling systems of the type described above store the cartridges in a two-dimensional array consisting of one or more vertical columns and horizontal rows. One or more disk or tape drives for the cartridges may be located anywhere in the array, but are usually positioned at the ends of the columns or rows. In any event, such a cartridge handling system will include apparatus for moving the cartridge engaging assembly throughout the array, so that the stored cartridges can be accessed and transported to and from the appropriate disk or tape drive.
While cartridge handling systems of the type described above provide a convenient means for automatically accessing a large number of cartridges, they are not without their problems. For example, a key factor in the successful operation of such a cartridge handling system is the ability to quickly and accurately move the cartridge engaging assembly throughout the array, engage a desired cartridge, and move it quickly to the appropriate cartridge reading device. Generally speaking, the apparatus for so moving the cartridge engaging assembly tends to be complex, and may include a large number of drive motors and position sensors to accomplish the desired functions. As with any mechanical system, however, such increased complexity often means decreased reliability. Therefore, it is desirable to minimize the number of components in such a system, but without sacrificing other performance parameters, such as speed and accuracy.
Another problem with such cartridge handling systems relates to the support and accurate positioning of the cartridge engaging assembly with respect to the cartridges stored in the array. For example, many cartridge engaging assemblies are cantilevered on a leadscrew, which when turned, moves the cartridge assembly across the array of cartridges. Unfortunately, such a cantilevered mounting arrangement tends to allow excessive transverse or rotational movement of the cartridge engaging assembly, which reduces positional accuracy. One way to increase the stability of the cartridge engaging assembly, thus positional accuracy, is to use rigid guide rails or tracks to provide additional support to the cartridge engaging assembly. Disadvantageously, many of the guide rail or track assemblies in use today are precision machined items, which adds to the overall cost of the cartridge handling system. Further, such guide rail assemblies are often difficult and time consuming to align. Worse yet, the guide rail assembly may be knocked out of alignment during subsequent shipping or movement of the cartridge handling device, thus requiring re-alignment and re-calibration before the device can be placed in operation.
Another problem relating to many cartridge handling systems is access speed, and efforts are constantly being made to minimize the mass of each component of the system, including the linear displacement and support apparatus for the cartridge engaging assembly, which tends to increase the speed at which the cartridge engaging assembly may be moved among the columns and rows of cartridges. Unfortunately, it is usually more difficult to achieve the desired degree of positional accuracy with a lighter weight system, and designers are constantly trying to find the optimum balance between light weight and positional accuracy. It is also desirable to minimize the volume requirements of the linear displacement and support apparatus so that it may be mounted in a relatively small space within the cartridge handling system.
Consequently, there remains a need for a cartridge handling system having increased positional accuracy to reduce errors due to misalignment of the cartridge engaging assembly. Such increased positional accuracy should be achieved with a minimum number of components to increase reliability, yet not require the use of expensive machined guide rails or tracks, which adds cost. Additional advantages could be realized by reducing the amount of time required to align and calibrate the assembly during production, and by reducing the likelihood of subsequent misalignment, such as may occur during shipping. Ideally, the above advantages should be accomplished without increasing the mass of the moving components, which tends to adversely affect access speed.